We used high-temporal resolution echo-planar imaging (TR=100ms) to characterize the time-course of the BOLD signal during the initial stimulus onset. This study clearly demonstrated the existence of a negative BOLD response during first 2-4s of the stimulus onset, in total agreement with the results reported by the optical imaging studies. In a more recent study, by taking advantage of the retrospective correction technique for removing physiological noise, we have conducted a more elaborate study of the early response, clearly demonstrating the ability of initial response mapping in individual subjects.